The invention relates to a fuel injection system for mixture-compressing, externally ignited internal combustion engines. The system includes a fuel distribution unit and fuel metering valves whose flow cross section is changed in unison to determine the fuel quantity delivered to the injection valves. The fuel metering takes place at a pressure difference which is held constant by a valve inserted in the fuel flow downstream of the metering valve. This valve has two chambers separated by a resilient member which can alter its flow cross section. There is one such valve in each of the fuel supply lines for the cylinders of the engine and, in each case, the first valve chamber experiences the fuel pressure downstream of the metering valve in the sense of valve opening and at least one of the plurality of valves is a pressure equalizing valve.
Fuel injection systems of this type are used for the purpose of maintaining a constant pressure drop and, thus, a precise fuel metering which is independent of the pressures ahead of and downstream of the fuel metering unit.
In a known fuel injection system of this type, the fuel for the individual cylinders of the internal combustion engine is metering out in unison by a control edge of a control slide cooperating with a plurality of control ports.
The metering process takes place at a constant pressure difference, held constant by equal pressure valves and a differential pressure valve. While the pressure difference is normally constant, it is possible to alter it in dependence on motor parameters by means of an electromagnet. In the known system, the differential pressure valve adjusts the control pressure acting on the equal pressure valves. A fuel injection system of this type permits a direct intervention at the differential pressure valve.